Mejzlik Propellers s.r.o. 18x6 2B MC

The Mejzlik 18x6 2B MC is a two-blade composite propeller made in the Czech Republic by Mejzlik Propellers s.r.o. for mid-sized multicopters, available for clockwise and counter-clockwise rotation. The designation gives diameter and pitch, 18 in and 6 in, and the blade count as 2B. It is made by wet layup.

The 6 in pitch is one third of the diameter and flat, laid out for hovering and efficiency at low rotational speed. Two blades keep efficiency higher than a multi-blade layout. The weight is 25 g with a tolerance of 10 per cent, and the propeller does not fold. The core diameter of the hub is 16.9 mm; there is no fixed bore, and the hole pattern follows the manufacturer's drilling guide. The maximum speed is 10,000 rpm, according to the datasheet the hover limit, bounded by blade-tip speed; in forward flight the limit drops. The maximum thrust of 12.3 kgf is simulated.

Legally the aircraft counts. Multicopters with 18 in propellers fall, depending on take-off mass, into class C2 or C3; the open category ends at 25 kg, classes C1 to C3 require direct remote ID, and from 250 g the operator must register. Commercial use does not change the category, which depends on the aircraft and the risk of the operation. Thrust and speed limit of a single propeller say nothing about take-off mass.

On selection: since no fixed bore is provided, the mounting must match the motor. With composite, watch for frayed edges, nicks at the tip and leading edge, and dull-sounding areas that point to delamination. Even small damage changes thrust and balance at 18 in. Clockwise and counter-clockwise versions are fitted as a pair on the motors.